1. Field of the Invention
Embodiments of the invention relates to the field of semiconductor, and more specifically, to lithography.
2. Description of Related Art
Extreme ultraviolet lithography (EUVL) is a new generation lithography that uses extreme ultraviolet (EUV) radiation with a wavelength in the range of 10 to 14 nanometer (nm) to carry out projection imaging. The EUVL system uses reflective optics and masks in which the image is formed in an absorbing metal.
The performance or throughput of the EUVL system may be degraded due to a number of factors. One such factor is the erosion in the multi-layer (ML) coating in the source collector optics. This erosion is believed to be caused by the highly energetic ions generated from the high power plasma source. If the ML coating is eroded, the EUV reflectivity is reduced leading to dose non-uniformity and throughput loss.